Pyrimidines. XIII. 2‐ and 6‐substituted 4‐pyrimidinecarboxylic acids

The “abnormal” behavior of 4,6‐dimethyl‐2‐pyrimidinol towards nitrous acid has been clarified. The reaction between 4‐methyl‐2‐pyrimidinol and nitrous acid has been utilized as a new synthetic procedure for the preparation of several 2‐substituted 4‐pyrimidinecarboxylic acids. 2‐Hydroxy‐4‐pyrimidinecarboxylic acid has also been prepared from 4‐chloro‐2‐methylthiopyrimidine via the trimethylammonium intermediate. 6‐Amino‐ and 6‐thio‐4‐pyrimidinecarboxylic acids have been readily prepared from the previously reported 6‐hydroxy‐4‐pyrimidinecarboxylic acid.